The Effects of Flood-induced Lane Reduction on the Capacity of a Road Network

Flooding can severely disrupt transportation infrastructure. Existing models for assessing flooding's impact on road transport often assume all lanes remain open, which contradicts actual observations. This study examines the impact of flood depth on road capacity and traffic conditions, aiming to enhance flood-based traffic models by analyzing the relationship between flooding and the Macroscopic Fundamental Diagram of Traffic. Fifteen (15) 30-minute video clips of flooded roads from the CCTV archive of the Metro Manila Development Authority (MMDA) were analyzed. Analysis of these videos showed that flood depths over 25 cm consistently caused lane closures. Moreover, empirical data from 433 samples revealed a significant reduction in vehicle flow, decreasing by 40% to 70% per lane kilometer as lane closures increased. These findings underscore the substantial impact of flood-induced lane closures on traffic flow and can be used as reference for future flood-based traffic models.